Tunable exchange bias in Hofmann MOF-derived α-Fe2O3/Pt magnetic composites

Abstract

The pursuit of strong, tunable, and thermally robust exchange bias (EB) is not only a fundamental scientific challenge but also a critical prerequisite for advancing spintronic technologies. Bottom-up designed nanostructures offer a versatile platform for engineering EB, owing to their precise control over composition, morphology, and assembly. However, studies on the EB effect in MOF-derived magnetic nanocomposites remain less unexplored. This study reports the EB effect in α-Fe₂O₃/Pt composites obtained via the pyrolysis of Hofmann-like Pt/Fe MOF at 450 °C, 550 °C, and 650 °C. The results show that Pt particles are dispersed on the α-Fe₂O₃ particles, forming α-Fe₂O₃/Pt composites. The magnetic properties of samples are characterized by zero-field-cooled (ZFC) and field-cooled (FC) susceptibility as well as hysteresis loop measurements. Notably, a significant EB effect is observed in all samples and the optimized sample pyrolyzed at 450 °C exhibits the largest H_EB of 2099 Oe at 2 K under a cooling field of 40 kOe, which exceeds that of pure α-Fe₂O₃ and other α-Fe₂O₃ based composites. These findings highlight the calcination temperature as a critical parameter for tailoring the EB effect in MOF-derived oxide/metal nanocomposites.